1.Field of the Invention
This invention relates to a printed circuit board having through-holes, and a method for producing the same.
2. Description of the Background
In the field of printed circuit boards, there is a tendency towards high density packaging for coping with miniaturization of electronic devices, and a so-called double-side printed circuit board is employed extensively, as shown in FIG. 10.
With the double-sided printed circuit board, a desired metallization pattern is provided on each of the substrate surfaces, and a through-hole 101 is formed through the substrate 102 at an optional position of the substrate.
Meanwhile, with the printed circuit board, chip components, such as chip resistances or chip capacitors, as packaging components, are mounted on a land 103 by soldering, such as by cream soldering. It is a frequent occurrence that molten solder flows into the through-hole 101 from land 103 during soldering where it is inadvertently contacted with the interconnection pattern on the back side to establish electrical connection to interfere with a normal operation.
A conventional practice for avoiding such problem has been to provide a small spacing between the through-hole 101 and the land 103a and to establish electrical connection by providing a connecting pattern 103a.
However, if the through-hole 101 is spaced apart from the land 103, the space on the substrate 102 occupied by these components is increased to retrogress from high density packaging of the printed circuit board.
For coping with such problem, a printed circuit board as shown in FIGS. 11 and 12 has been proposed.
The printed circuit board, shown in FIG. 11, is provided with a through-hole 105 in a land 106 which is reduced in size. Besides, as shown in FIG. 12, a solder resist 107 is provided on the back side of the substrate 102 for stopping the through-hole 105.
In such case, should the solder flow into the through-hole 105 during soldering a chip component 104 to the land 106, it cannot occur that the solder be allowed to flow onto the back side of the substrate.
However, since the solder resist 107 is provided on the back side of the substrate 102, it becomes impossible to mount chip components on the back side of the substrate, as a result of which the number of the components that can be mounted is decreased to retrogress from high density packaging of the printed circuit board.